Study To Increase The Safety Ratio Of Boom And Arm Connection Pin For20t Excavator

This thesis aims to study the countermeasure about boom and arm connection pin break problems of20t excavator in the market. It mainly considers the problem on the points of design strength of the pin, the heat treatment performance of pin materials, the statistic method of durability life in actual and so on. And finally increase the actual durability life obviously, while decrease the failure rate of pin breaking in the market.As we know, the construction machinery and equipments are usually used for the construction of infrastructures, such as the railway road, the port, and the public constructions. Along with the high speed development of the internal infrastructures, the requirement of construction machinery, especially the excavators, were also ushered in substantial growth.According to the statistic data, the overall sales quantity of excavators had raised from78thousands sets at the year2008to180thousands sets at the year2010. When to the actual work status, the earth-rock digging and loading work quantity raised variously. Some of the working field had transferred the equipment from loading machinery to total excavators(the ratio of excavators/loaders had increased from0.57:1at2006to0.68:1at2009).During the working process of digging and loading, especially the rock work status, the excavator’s pin of work equipment endures heavy working duty. The durability of which have significant influence for the whole machinery performance.So as that, how to decrease the occur rate of the failure and make sure the successive working hours, as well as to lengthen the interval between failures, have very important practical implications to the heavy duty excavators.This thesis studied the actual failure problem of pin breaking occurred in the market. Two kinds of typical pin breaking mode were summarized according to the many fault fracture occurred in the market. One mode is that because of the insufficient heat treatment performance caused during the heat-treatment process, which lead the pin to the start of breaking when endure the load. Another mode is because of the early fatigue crackle during the very heavy duty cycle, which mainly occurred during rock duty, although for this mode the heat treatment performance of the pin were satisfy the requirements.During the seeking process for the countermeasure to response the pin breaking problem, we investigated the strengthen and practical performance of these popular pin material at domestic and even abroad. At the same time, the academic research for the pin of excavator working device are grasp not only at home but also internal ones. These understanding for the research direction of the ongoing subjects and its achievements was clear the advancement on this area, and decided that this theme as the thesis’s topic finally.As a research for the countermeasure of pin breaking problems, the mainly process is listed next. Firstly, we take some measure for the stability of the pin’s heat treatment performance based on the on holding of actual heat treatment performance, and gained certain improvement effect. Secondly, from the source of short durable life, based on the actual status, we hypothesis the mechanical analysis model to calculate the actual strength data. And then try to raise the safety ratio of the pin and analysis the feasibility of durability improvement. Thirdly, we transfer the feasibility into application, and achieved excellent results by the way of using high strength materials.As a thesis, there are some improvements compared with the published thesis lies as follows.Firstly, this topic comes directly from the actual problem, is a solving research of special problem. Also, the technology is the leading items at current stage in excavator industry.Secondly:technical achievements and the previously published papers are confined to the scope of the study theory. But this time, besides the basis of theoretical research, has been implemented the research results come true constantly, and through the long track, made extensive useful data, which verify the theoretical research results from a statistical perspective.Thirdly, procedure. As a production plant, the processing for all kinds of business has its own characteristics, and the specific business processes also have deep enterprise culture. Therefore, the treatment on the issues always has its own program, and follow its prescribed order, one after another, the input of manpower and material resources have effect the implement in the product speedy, which ensured the research thoroughly, and continued.In conclusion, this thesis has successfully solved the excavator boom and arm connecting pin breaking problems in the market. Out of the necessary of technology secret, some of the key data are handled. But the research methods, and the process during the way to countermeasure the failure, is believed have certain reference significance for the same problems.